Open versus robot-assisted retroperitoneal tumors resection involving inferior vena cava, abdominal aorta, and renal hilum: a comparative study

Introduction Surgery is currently the only effective treatment for retroperitoneal tumors that do not involve any specific organ. The use of robots for removing both benign and malignant retroperitoneal tumors is considered safe and feasible. However, there is insufficient evidence to determine whether robotic retroperitoneal tumor resection (RMBRs) is superior to open retroperitoneal malignant resection (OMBRs). This study compares the short-term outcomes of robotic excision of benign and malignant retroperitoneal tumors with open excision of the same-sized tumors. Methods The study compared demographics and outcomes of patients who underwent robotic resection (n = 54) vs open resection (n = 54) of retroperitoneal tumors between March 2018 and December 2022. A 1:1 matching analysis was conducted to ensure a fair comparison. Results The study found that RBMRs resulted in reduced operative time (OT), estimated blood loss (EBM), and postoperative hospital stay (PSH) when compared to OBMRs. Additionally, RBMRs reduced EBL, PHS, and OT for patients with malignant tumor involvement in major vessels. No significant differences were found in tumor size, blood transfusion rate, and morbidity rate between the RBMRs and OBMRs groups. Conclusion When comparing RMBRs to OMBRs, it was observed that RMBR was associated with lower (EBL), shorter postoperative hospital stays (PHS), and reduced operative time (OT) in a specific group of patients with both benign and malignant tumors. Supplementary Information The online version contains supplementary material available at 10.1007/s00464-024-10848-1.

impact treatment outcomes [3][4][5][6][7].The retroperitoneum is a rare site for tumor growth, which can arise from various soft tissues and affect retroperitoneal organs.Retroperitoneal tumors can be benign or malignant, with malignant tumors further classified into those originating from epithelial tissues and those arising from non-epithelial tissues.Liposarcoma, leiomyosarcoma, and undifferentiated pleomorphic sarcoma are the most common subtypes.Certain types of sarcomas are more common in children, while diseases characterized by lymph node enlargement primarily affect adults.It is important to acquire a reliable diagnosis before considering surgery because the therapeutic techniques, including medical and surgical treatment, of malignant and benign tumors and the type and scope of surgery might differ significantly among the various kinds of tumors.A large number of benign and malignant tumors are eradicated through a laparotomy, which extends the hospital stay following surgery, postoperative agony, and delays healing [8][9][10][11].A reliable diagnosis is crucial before surgery, as treatment options for malignant and benign tumors vary significantly.Robotic techniques are increasingly used in retroperitoneal surgeries due to limited space and advanced surgical equipment.These techniques have a shorter learning curve and result in better postoperative recovery, less blood loss, and shorter operation times compared to open surgeries [12] Robotic resection for tumors has limited published reports, mostly case studies.Despite advancements in robotic techniques, research on this topic is still limited [13][14][15][16][17][18].Our study aims to compare the outcomes of robotic and open excision of retroperitoneal tumors.We hypothesize that robotic-assisted techniques will result in less operative time, bleeding, and postoperative complications, as well as minimal recurrence of tumors.

Patients and methods
We conducted a cross-sectional study to analyze the outcomes of surgical treatments performed between March 2018 and December 2022.During this period, we performed robotic resection on 104 patients and open resection on 68 patients.Before the surgery, experienced surgeons evaluated each patient to determine the best surgical option (robotic or open).All patients who were registered for the study were considered suitable candidates for both robotic and open surgery.They were given detailed information about the benefits and drawbacks of each surgical approach before making their final selection.There was no difference in tumor size between both groups.In this work, we applied propensity score matching to mitigate selection bias.Following the matching process, there were no obvious differences in demographic characteristics between the robotic and open groups.Patients provided their informed consent before the surgery and gave written consent for this study afterward.To compare the outcomes of robotic and open surgeries, we conducted a study with 1:1 propensity score analysis and telephonic interview were also performed.We matched 54 patients who had robotic surgery with 54 patients who had open surgery based on age, sex, BMI, ASA score, tumor size, and the procedure itself.The hospital ethical committee approved and registered this study.

Preoperative evaluation
Retroperitoneal tumors are detected through imaging and histological analysis.Ultrasound is the first method used, but its subjectivity is a drawback.Contrast-enhanced CT is preferred for assessing and staging primary retroperitoneal masses.Radiological indicators help establish a differential diagnosis, including the beak sign, phantom organ sign, embedded organ sign, and prominent feeding artery sign.CT angiography or 3D reconstruction is used for preoperative evaluation and surgical planning.

Inclusion and exclusion
To be eligible for inclusion, the patient must be between 18 and 82 years old, have a resect able retroperitoneal tumor (malignant or benign), and not have any medical conditions that would make anesthesia or surgery unsafe.Exclusion criteria include tumors bigger than 10 cm, no evidence of tumor involvement in the retroperitoneal organs, and severe cardiopulmonary or hepatorenal insufficiency.Surgery may still be considered if the tumor is adhering to major blood vessels.

Perioperative data
Data from preoperative and pathology records, along with baseline demographics, were collected.The following parameters were analyzed: operation time, estimated blood loss, blood transfusion, conversion to open surgery, postoperative complications, and PHS.Mortality and readmission rates within 1 year were also investigated.Pathology records were examined for tumor information.

Surgical technique and follow-up
RBMR surgeries were performed by an experienced team with over 1000 robotic procedures using the Da Vinci Xi Surgical System.The same team performed both robotic and open surgeries.For robotic resection the patient was positioned in the left lateral decubitus position with the right side elevated approximately 70 degrees during the surgery.They were under general anesthesia and continuously monitored with central venous and arterial pressure monitoring Fig. 1.
To ensure an open approach, the patient is carefully placed in the right lateral Jackknife position at a 90-degree angle.The support for this is provided by both a beanbag and an axillary role.To ensure protection, the left arm is equipped with ample padding as well as an airplane-type retractor.It is important to secure the left arm such that the scapula rolls anteriorly.The incision will be made overlying the 11th or 12th intercostal space and extended toward the umbilicus.The position shifted in accordance with the tumor's left or right location.Follow-up data was collected through outpatient departments and phone interviews.In the first year, patients underwent clinical examinations, blood tests, and imaging every 3 months.

Statistical analysis
Continuous data were reported as either mean SD or median based on their distributions.Categorical data were compared using the chi-square test.To reduce the impact of possible confounders and selection bias, propensity score analysis was used to match covariates such as age, sex, body mass index (BMI), ASA score, tumour size, and tumour involvement to major blood vessels between the two groups.A 1:1 nearest neighbour matching method was used to select individuals for each group.All statistical tests were performed using SPSS v22.0 (SPSS Inc., Chicago, IL, USA).A p-value of less than 0.05 was considered statistically significant.

Results
During the study period, 172 patients (104 RBMR and 68 OBMRs) had retroperitoneal benign and malignant tumors excision.Patients in the OBMRs group had a bigger tumors size and more blood transfusions than those in the RBMRs group before matching.In this propensity score matching trial, 54 patients RBMRs and 54 patients received OBMRs.After matching, there were not any significant differences in demographic variables between the two groups.

Pathological and postoperative outcome
Upon final histological inspection, it was found that the tumors in both groups were a mix of benign and malignant.Table 1 shows that both groups had similar pathology.Table 2 displays the perioperative results for both groups.The robotic group had significantly reduced surgical time (p = 0.004), lower estimated blood loss (p = 0.008), and shorter postoperative hospital stay (p = 0.001) compared to the open group.There was a significant postoperative complication, with 3 patients from each group experiencing lymphatic leakage and receiving treatment in accordance with hospital guidelines.Both groups had similar rates of blood transfusion (p = 0.7504).All patients underwent effective robotic removal of both benign and malignant tumors located in the retroperitoneal region, with no need to switch Fig. 1 Port placement for robotic tumor excision.Trocar placement for the surgery.A six-trocar technique was applied for the surgery.One 12 mm trocar near the umbilicus was the designated camera port (point C).Camera port, robot arm port 1 (near the liver margin) and 2 (above the anterior superior iliac spine) formed approximate 120 angular degree.Assistant port A1and A2 were 8cm from the camera port.A 5 mm trocar under the liver margin near the midclavicular line was used as the assistant port for liver retraction (point A3) to laparotomy.The mortality rate in both groups was 1.8%.There were no patients who needed to undergo another operation or were readmitted to the hospital within 1 year.

Clinical outcomes of malignant tumors involvement the major vessels
Table 3 summarizes the characteristics of patients with malignant tumors involving major vessels before undergoing surgery.The data shows that both the Robotic and Open surgery groups had similar age, sex, BMI, and tumor size.They also had comparable rates of blood transfusion, illness, and mortality.The rates of positive surgical margin, local recurrence, adjuvant chemotherapy, radiotherapy, and target therapy were all similar between both groups.However, there were significant differences between the two groups in terms of estimated blood loss (EBL) (p = 0.0221), postoperative hospital stays (PHS) (p = 0.0001), and operation time (OT) (p = 0.0023).

Discussion
The findings of our study Robotic surgery group compared to the open surgery group.The robotic group showed significantly reduced PHS, intraoperative blood loss, and operating time.Increased accuracy and delicacy during manipulation may lessen surgical harm.All RBMRs in this study were performed exclusively utilizing the fully robotic method, without any need for conversion to open surgery.All patients who were registered for the study were considered suitable candidates for both robotic and open surgery.They were given detailed information about the benefits and drawbacks of each surgical approach before making their final selection.
There was no difference in tumor size between both groups.
In this work, we applied propensity score matching to mitigate selection bias.Following the matching process, there were no obvious differences in demographic characteristics between the robotic and open groups.Robotic surgery has gained popularity due to its ability to enhance manipulation capabilities, provide better visibility, and enable rapid bleeding management.It also decreases injury to the gastrointestinal system and expedites the recovery of gastrointestinal function as compared to open surgery [19][20][21][22][23][24].Additionally, the results after surgery are consistently getting better and it is widely accepted.Robotic surgery is rapidly becoming the preferred method in urology experiencing substantial growth in industrialized countries.That they have exceeded the outcomes of traditional open surgery for most treatments [25].Robotic resection techniques are safe and feasible for removing retroperitoneal tumors, including large tumors or those attached to major blood arteries, with no significant negative impact on perioperative outcomes [26].Due to the greater probability of malignant retroperitoneal tumors invading major vasculature, we further categorized the patients based on the tumor type.[32,33].As surgeons gain more experience in operating robotic systems, they tend to become more efficient, which results in shorter operative times.Robotic systems provide better precision, dexterity, and visualization when compared to traditional open surgery, which allows for more accurate and efficient complex procedures.However, there may be a learning curve for surgeons and their teams when adopting robotic surgery.As the experience of surgeons increases, the time taken for operations tends to decrease.Moreover, this study has shown that there were statistically significant differences in the blood transfusion rates between the two patient groups.

Limitations
This study has several limitations, including a relatively small sample size, limited evaluation of long-term outcomes, and lack of information about the surgeons' experience level with robotic surgery.Additionally, the study did not evaluate the cost-effectiveness of robotic surgery or potential confounding factors that may impact the outcomes.Future studies should address these limitations by conducting largerscale investigations that evaluate the long-term effects of robotic surgery on patients, assess the cost-effectiveness of the procedure, and account for potential confounding factors.Furthermore, future studies should evaluate the feasibility and safety of robotic surgery for retroperitoneal tumors in a variety of settings and patient populations.By addressing these limitations and exploring future perspectives, researchers can continue to improve the outcomes and accessibility of surgical treatments for retroperitoneal tumors.

Conclusion
In conclusion, our findings show that RMBRs are as safe and effective as OMBRs in patients with retroperitoneal benign and malignant tumors.With the benefits of the robotic approach, RMBRs may offer significant improvements over OMBRs, reducing OT, EBL and PHS in patients even for tumors involving major vessels.

Table 1
Comparison of robotic group and open group: patients characteristics Values represent mean ± SD, or N (%).Boldface represents statistically value